Three of the defendants ? Larry Collins, of Golden Meadow, Richard Autin, of Houma, and Kevin Larousse, of Hattiesburg, Miss. ? face prison terms of up to five years after pleading guilty Tuesday to conspiracy charges. Woody Collins, of Lockport, pleaded guilty to misprision of a felony and faces a maximum of three years imprisonment.

Autin was facilities manager in Port Fourchon for Newpark Resources Inc. The other defendants owned and operated a company providing contract laborers to Newpark.

Federal prosecutors say the latter company employed Autin's wife and son in return for allowing Larry Collins and Larousse to bill Newpark for fraudulent time based on fictitious employees.

An Iranian military observation aircraft flew within 50 yards of an armed U.S. Navy helicopter over the Persian Gulf this month, sparking concern that top Iranian commanders might not be in full control of local forces, CNN has learned.